sometimes this play is just to establish the leader of the pack. Remember dogs are pack animals. Just watch for signs of her going into heat. MY female was 9 months old when we got the male who was 12 weeks old. at first she mothered him coddled him and snuggled. as he grew and tried to dominate her then she told him who was boss. the only thing had worried me about this behavior is sometimes she got a little aggressive and would nip and bit into his nose and drew blood a couple times from his nose. I would crate her and baby him. When I would let her out she would go back to playing.